1. Field of the Invention
The present invention relates to a centrifugal type blower having a centrifugal multiblade fan, and is effectively applied to a blower in an air conditioning system for a vehicle.
2. Description of Related Art
A centrifugal type blower which limits upsizing of a casing and seeks to reduce a noise which is generated as a result of the impingement of air blown out of a fan against a nose part is disclosed in JP-A-2002-339899 (corresponding to US2002/0131861A1).
This centrifugal type blower accommodates a fan and includes a casing having an inlet for air on one end side of a rotatable shaft in its axial direction and having an involuted air passage along an outer circumference of the fan. This casing is formed such that a size of the casing from an outer edge of the fan to a side wall part of the casing on the inlet side is smaller than a size of the casing from the outer edge to the side wall part on the counter-inlet side within a predetermined range from the nose part toward a volute end side of the casing.
Accordingly, since a range which satisfies such a dimensional relationship is set only in the predetermined range, a good balance is achieved between reduction in the noise which is generated as a result of the impingement of air blown out of the fan against the nose part with the upsizing of the casing limited, and inhibition of decrease in an amount of air blown caused by making large the size of the casing from the outer edge of the fan to the side wall part of the casing at the nose part, in comparison with the whole region from a volute start to a volute end of the casing.
Nevertheless, further reduction in the noise which is generated as a result of the impingement of air blown out of the fan against the nose part with the upsizing of the casing limited, is required for such a centrifugal type blower.